Sets SystemUsesLightTheme = 0 so the taskbar, Start menu and system surfaces use the dark theme. Per-user; reversible.
MaxTweaks applies this tweak with one click and snapshots your original setting first, so you can revert it cleanly at any time. A System Restore point is offered before batch changes, and every tweak links to its official source.
Get MaxTweaksOfficial documentation: https://learn.microsoft.com/en-us/windows/apps/desktop/modernize/apply-windows-themes